Glucan binding protein C of Streptococcus mutans mediates both sucrose-independent and sucrose-dependent adherence

Joshua L. Mieher, Matthew R. Larson, Norbert Schormann, Sangeetha Purushotham, Ren Wu, Kanagalaghatta R. Rajashankar, Hui Wu, Champion Deivanayagam

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

The high-resolution structure of glucan binding protein C (GbpC) at 1.14 Å, a sucrose-dependent virulence factor of the dental caries pathogen Streptococcus mutans, has been determined. GbpC shares not only structural similarities with the V regions of AgI/II and SspB but also functional adherence to salivary agglutinin (SAG) and its scavenger receptor cysteine-rich domains (SRCRs). This is not only a newly identified function for GbpC but also an additional fail-safe binding mechanism for S. mutans. Despite the structural similarities with S. mutans antigen I/II (AgI/II) and SspB of Streptococcus gordonii, GbpC remains unique among these surface proteins in its propensity to adhere to dextran/glucans. The complex crystal structure of GbpC with dextrose (β-D-glucose; Protein Data Bank ligand BGC) highlights exclusive structural features that facilitate this interaction with dextran. Targeted deletion mutant studies on GbpC's divergent loop region in the vicinity of a highly conserved calcium binding site confirm its role in biofilm formation. Finally, we present a model for adherence to dextran. The structure of GbpC highlights how artfully microbes have engineered the lectin-like folds to broaden their functional adherence repertoire.

Original languageEnglish (US)
Article numbere00146-18
JournalInfection and Immunity
Volume86
Issue number7
DOIs
StatePublished - Jul 1 2018
Externally publishedYes

Keywords

  • Antigen I/II
  • Fibrillar
  • Glucan binding protein
  • Lectin-like fold
  • Microbial adherence
  • Polyproline type II helix
  • Salivary agglutinin
  • Streptococcus gordonii
  • Streptococcus mutans
  • Sucrose-dependent adhesion
  • Sucrose-independent adhesion

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

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